Oilpressure Bristol and backfire

[justnow]

Driven yesterday at the hottest Day  my Car developed two new issues. Fristly after about 100 miles oilpressure at 3000rpm was around 50 and at idle just 20. Almost like the Oil I am using (Castrol 20W50). This morning it was fine again. Do I need to adjust oilpressure? Secondly I adjusted valve clearance, all carbs are freshly overhauled and I just replaced the centre part of the exhaust system. But when really hot (yesterday oiltemperature was around 190 Fahrenheit) engine revs very reluctantly but once above2000 rpm there is lots of power and it easely revs until 5500. When slowing down quite some little explosions develop in the exhaust. Sounds nice for a while but I would like to stop this. Any recommendations? Thank You Wilhelm BEX 312

[AC Ace Bristol]

.
   Wilhelm.
   
   The Oil is getting very hot and getting thin (Change in Viscosity) recommend you fit a oil cooler which will auomatically cut in and cool the oil in summer, whilst the valve in the Vokes oil pump housing will not open in cold winter climate.
   
   When the engine gets very hot the brass banjos to each carb expand and crush the fibre washer, when engine cools you could experience fuel leaking as the fibre washer will not return to its original thicknesss.
   
   
   running very hot you can also experience vapourisation, which will be emore evident at low RPM.
   
   Exess fuel in the exhaust is detonating causing bakefire on overrun, this is often experienced when changing down at speed as the fuel is not being fully burnt in the cylinder head.
   
   Just a few comments for others discuss.[;)]
   
   Keith

[justnow]

Great Keith and thank you. Just checked for Fusel leakage. Luckely okay. Do you think 190 Fahrenheit is too high?

[Flyinghorse]

190f is about 87degc which does not sound to hot,but the viscosity of the oil will drop with temperature. If you look at the Castrol classic technical specs for 20w50  the viscosity does drop with temperature,so logically an oil cooler will bring it back up.
   Viscosity, Kinematic
   40C
   ASTM D445
   mm²/s
   157.71
   Viscosity, Kinematic
   100C
   ASTM D445
   mm²/s
   17.3
   The issue in adjusting to compensate for when hot ,will be when cold you may have excessive oil pressure which is not good either/you have to take care till warmed up.
   I would adjust to suit the type of driving you do the most,but in the back of my mind it should likley bet set for "operating conditions,and not cold settings as per Bristol procedures,but then someone with correct advice will be along later.
   One other thought is that you are running the standard oil pump rotors,and could/should upgrade to the MGB rotors. There was an article (i could email) ,and I did this to my Bristol 400 oil pump (Using a 100d2 pump body ) and have much improved oil pressure now.
   
   Re the backfire and no power below 2000rpm (and this is based on Bristol 400 85c engine experience) --I would check the distributor timing advance base plate is functioning & dist body earthed(400 has sliding manual advance/retard as well),and as you have put new carbs on,the float heights--you need to make a tool to fit in the carb body to get all fuel levels correct,as the engine is sloping front to back as it sounds like the carbs are not coming of the idle circuit onto the main circuit smoothly.Carb balancing is also worth checking. I also made new gaskets where the carb body meets the head and used hylomar to stop any leaks there that might weaken the mixture.
   
   Graham

[justnow]

Just a quick update. Will install an oilcooler and hope to cure the issue with oil pressure. Last few days at not so hot temperatur all was okay. Keith was right with the fibre washers. One is leaking and I will need to replace it.